Capacitance sensors are used in a wide variety of applications, and are used in measuring force, pressure, liquid levels, inclination, positional information (such as distance, displacement, motion, and acceleration), and hosts of other purposes. Capacitance sensors/sensing systems that respond to charge, current, or voltage can be used to detect position or proximity (or motion, presence or any similar information), and are commonly used as input devices for computers, personal digital assistants (PDAs), media players and recorders, video game players, consumer electronics, cellular phones, payphones, point-of-sale terminals, automatic teller machines, kiosks and the like. Capacitive sensing techniques are used in applications such as user input buttons, slide controls, scroll rings, scroll strips and other types of inputs and controls. One type of capacitance sensor used in such applications is the button-type sensor, which can be used to provide information about the proximity or presence of an input. Another type of capacitance sensor used in such applications is the touchpad-type sensor, which can be used to provide information about an input such as the position, motion, and/or similar information along one axis (1-D sensor), two axes (2-D sensor), or more axes. Both the button-type and touchpad-type sensors can also optionally be configured to provide additional information such as some indication of the force, duration, or amount of capacitive coupling associated with the input. Examples of 1-D and 2-D touchpad-type sensors based on capacitive sensing technologies are described in United States Published Application 2004/0252109 A1 filed by Trent et al. and U.S. Pat. No. 5,880,411 issued to Gillespie et al. on Mar. 9, 1999. Such sensors can be readily found, for example, in input devices of electronic systems including handheld and notebook-type computers.
A user generally operates capacitive input devices by placing or moving one or more fingers, styli, and/or other objects near a sensing region of the sensor(s) located on or in the input device. This creates a capacitive effect upon a carrier signal applied to the sensing region that can be detected and correlated to positional information (such as the position(s) or proximity or motion or presences or similar information) of the stimulus/stimuli with respect to the sensing region. This positional information can in turn be used to select, move, scroll, or manipulate any combination of text, graphics, cursors, highlighters, and/or other indicators on a display screen. This positional information can also be used to enable the user to interact with an interface, such as to control volume, to adjust brightness, or to achieve any other purpose.
Although capacitance sensors have been widely adopted, sensor designers continue to look for ways to improve the sensors' functionality and effectiveness. In particular, it is continually desired to simplify the design and implementation of such sensors. Moreover, a need continually arises for a highly versatile yet low cost and easy to implement sensor design. In particular, a need exists for a sensor design scheme that is flexible enough to be easily implemented across a wide variety of applications yet powerful enough to provide accurate capacitance sensing, while at the same time remaining cost effective.
Accordingly, it is desirable to provide apparatus, systems, and methods for quickly, effectively, and efficiently detecting a variable capacitance. Moreover, it is desirable to create a scheme that can be implemented using readily available components, such as standard ICs, microcontrollers, and discrete components. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.